How to Chop an Onion – 2 Ways to Dice an Onion

If you haven’t already, please make sure you’re familiar with basic knife safety before starting this tutorial. (link) Please remember to give onions special consideration because of their shape, texture, and tendency to make your eyes water!

We’ve been gradually reducing the size of our onions – going from onion chunks (link), to onion slices (link), and now diced onion! Dicing onions is a great way to get a lot of flavour out of them in a short cooking time.

This tutorial contains two different methods to dice an onion. The first method is simpler, but it does take a little time. The second is so fast your eyes barely have time to water, but it is a more advanced technique.

Method 1

Start by chopping your onion into slices. Just follow the tutorial from last month (link), although you can skip cutting the onion into quarters and just slice the halves.

Once you have your slices, lay them down to dice. I like to cut a sort of lazy grid pattern, but you could also cut it into triangles (sort of like a mini pizza; see picture below).

Hand drawing of two onion slices with cutting guidelines (grey dotted lines)

To save time, you can cut through multiple slices at once. I would recommend you start with just one and work your way up slowly to find how many slices you’re comfortable chopping at once. Make sure if you’re stacking slices that you have the largest one on the bottom and the smallest on the top – it’s important that your stack doesn’t fall over during cutting.


Method 2

I actually learned this second technique from the anime sweetness & lightning. It’s a little tricky, because it involves breaking my second rule of knife safety (see my earlier post here). But it’s so much faster that I’ve diced onions this way ever since.

To start, remove the skin and top of the onion, but leave the root end on. (This will help the onion stay together as you chop it.) Cut the onion in half.

Hand drawing of half a red onion, peeled but with the root end still attached

Next, cut into the onion towards the root end. You don’t need to cut all the way through, but you’ll need to use your non-knife hand to steady the onion.

Hand drawing of half a red onion with cutting guidelines (grey dotted lines)

Now cut downwards. You don’t need to cut right to the edges, because of the layers in the onion. I usually find just three cuts is plenty.

Hand drawing of half a red onion with cutting guidelines (grey dotted lines)

Finally, cut as if you were slicing the onion. Perfectly diced pieces of onion will simply fall off the end!

Hand drawing of half a red onion with cutting guidelines (grey dotted lines)

As you get towards the end of the onion, you may find that it starts to fall apart a bit. Hold it together if you can, but you can always deal with those parts that do fall off separately.

This technique definitely takes a bit of getting used to, but if you can master it it’s so worth it!


Diced onions can be used to add flavour to a huge variety of dishes, including stews, soups, and curries. They’re especially great in dishes where you want a little bit of everything in every spoonful.

You can fry diced onions in about 15-25 minutes, although it rather depends on how soft you like your onions! Onions can be eaten raw, or very well-done, so it’s really a matter of taste.

Bonus Post – How to Break The Second Rule of Knife Safety… Safely?!

You may have noticed that, at the start of every “How to Chop” tutorial, I keep plugging my post on knife safety. In fact, if you haven’t read it yet, here it is again (link).

The reason basically boils down to, I would hate for anyone to get hurt. And, particularly relevant to this blog, I would hate for anyone to be put off learning to cook because of it. But I have a slight confession to make: I break my own rules of knife safety.

Are you shocked? Anyway, the rule that I break on a regular basis is rule #2 – Always Cut Away from Yourself.


Now if you are going to break rule #2 of knife safety, it’s extra important that you have a good, sharp knife (rule #1). (I would also recommend you use a smooth, rather than a serrated, blade.) I know it seems counterintuitive, and I don’t mean razor-sharp, but you need to be able to push your knife through whatever you’re chopping with gentle pressure.

Which brings me to my second point – don’t slice. The type of motion you use with a knife will make a big difference to how safe it is. You are unlikely to cut yourself using just gentle pressure, but if you use a back-and-forth, sawing motion you probably will.


The safest way to cut towards yourself is actually to use your knife and thumb like a pair of scissors. This is a great way to peel or cut the blemishes out of vegetables. (My mum taught me this technique after I found out the hard way that I’m no good with a kitchen peeler…)

To make a ‘scissor grip’, hold the handle of the knife in the palm of your hand. Support the back of the blade with your forefinger for control, and use your other three fingers to make sure you have a solid grip. You can then use your knife and thumb like a really flexible pair of scissors! Why not try out the grip and pincer motion a few times to see how it feels, and if you want to try it on a vegetable?


If you are just getting to grips with basic knife skills, you may want to save this one for later. (I certainly didn’t start out breaking any rules – I was already quite confident with a kitchen knife before I tried this one!) But if you can master this technique, it can help you cook faster, and quite possibly freak out your friends in the process…